Magnetic welder&#39;s ground clamp



Nov. 29, 1949 K. A. BLIND MAGNETIC WELDER S GROUND CLAMP Filed Dec. 18,1947 1N VEIY TOR.

MW}: MW

A 770 E/VEVS.

Patented Nov. 29, 1949 UNITED STATES PATENT OFFICE MAGNETIC WELDERSGROUND CLAIVIP Karl A. Blind,v Thicnsville, Wis assignor to-DingsMagnetic Separator 00;, Milwaukee, Wis.,. a

corporation of Wisconsin.

Application December 18, 1947, Serial No. 792,558

'7 Claims. 1.

This invention relates in general to improvements in current groundconnectors as used by electric welders, and relates more specifically toimprovements in the construction and operation of magnetically actuatedelectric welders ground clamps. Many different types of current groundconnections and attaching clamps for electric welding use, haveheretofore been proposed and utilized commercially with varying degreesof success, and in some of these prior devices it has also been"proposed to employ a permanent magnet for the purpose'of holding theground terminal in contact with a grounded body such as a piece of work.In order toprevent excessive loss of time, these grounding clamps mustbe quickly and conveniently applicable and removable, but in order tofunction: properly while in actual use they must also provide a mostefiective electrical connection between the ground terminal and thegrounding body. Since these ground connectors are ordinarily subjectedto considerable abuse they must also be sturdily constructed withoutunnecessary complication, and the prior devices of this type did notmeet all of these requirements since most of them were eithercumbersome, costly, difficult to apply and remove, or failed to provideasuitable connection;

It is therefore an object of my present invention to provide an improvedmagnetic welders ground clamp which besides being simple and durableinconstruction, may be readily manipulated to provideefiectiveelectrical ground connections;

Another object of the present invention is to provide an improved grounddevice for welders; which is operable by one-ormore-perman'ent magnetsto automaticallyestablish an efiicient ground "when applied toagrounding body.

A further object of this invention is tcr provide a compact weldersground connector adapted to eifectively withstand normal abuse, andwhich may be-rapi'clly and e'asily'appliedto-the-work and removedtherefrom.

Still another object" of the invention' is to provide an: improvedelectric ground clamp adapted for diverse uses, and which maybe readilyconstructed. of relatively few: simple parts and sold at moderate cost.

An additional object of my invention: is to provide an improvedmagnetically actuated ground clamp: for welding equi'pmentor the like,which wlll'mosiz effectively hold the terminal in contact,withthegrounding bodywhile being-J conveniently removable. therefroim zThese and other objects and advantages of the invention willbe apparentfrom the following detailed description. A clear conception of thefeatures constituting my present-improvement, and of the mode ofconstructing and of utilizing several typical embodiments of theinvention, may be had by referring to the drawing accompanying andforming a part of this specification wherein like reference characters,designate the same or similar parts in the various'views.

Fig; l is a topview'of one typical embodiment of my improvedmagnetically actuated ground clamp wherein the terminal is su-rroundedby the magnet assemblage;

Fig. 2 is a central vertical section through the clamp and termlnalunit'of Fig. 1-, taken along the line 22;

Fig; 3 is a bottom view of the unit shown in Figs. 1 and 2-; and

Fig. 4 is a central vertical section througha modified typical clamp andterminal unit of the type wherein the terminal surrounds the magnetassemblage;

While the invention has been illustrated and described herein as beingadvantageously applicable to welders ground clamps operable by means ofseveral permanently magnetized slugs or blocks of special metal such asAlnico containing aluminum, nickel, cobalt, copper and iron, it is notmy desire or intent to unnecessarily restrict the scope or utility oftheimprovement by virtue of this limited disclosure;

Referring to Figs. 1 and 3 inclusive of the drawing, the ground clampwith internal terminal disclosed therein, comprises in general, acircular backing plate 1' having a central opening 8 and a tubularelement! of somewhat larger internal diameter than the opening 8 securedto and projecting away from'one side of the plate 1, both the plate 1and the. element 9 being formed of electrical.insulation; a groundterminal l0 slid- .ably penetrating the plate opening 8 and having oneend adapted for attachment to a conductor H whilexits opposite contactend is provided with a head I2 slidable within the sleeve element 9 andits medial portion is embraced by a helical compression spring l4coacting with the head l2 and reacting. against the plate I; outer andinner coaxial annular cup-shapedpole-pieces l5, I6 respectively havingfiat annular pole faces lying in a common plane, and being secured tothe oppositeend's of a series of magnetized cores or blocks I1; andscrew bolts. l8.firmly-'attaching the polepieces [5; IE to the backingplate 1 and simul- 3 taneously clamping these pole-pieces against theintervening magnet blocks ll.

The backing plate I and the sleeve element 9 may be formed of anydurable electrical insulating material such as synthetic resin, hardrubber, or the like, and these parts may be permanently united in anysuitable manner with the bor of the sleeve disposed coaxial with theopening 8. The ground terminal H) which is slidably confined within theopening 8 and element 9, may be formed of copper or copper alloy, andthe contact face of the terminal head I2 is preferably covered with a,protective layer or coating of silver or the like. The conductor I l isordinarilly a flexible insulation covered cable having its end providedwith a terminal fitting l9 which is firmly attached to the outer end ofthe terminal l6 and is clamped against a terminal stop washer by meansof a nut 21 and a lock washer 22.

The stop washer 20 v,coacts with a shoulder formed upon the terminal l0and is so located relative to the terminal head 12, that when the groundclamp is not in use the contact surface of the head l2 will be forcedoutwardly beyond the common plane of the faces of the pole-pieces l5,

I3 by the spring I4 and the washer 23 will then engage the backing plateI.

The outer and inner annular cup-shaped polepieces l5, l6 may beconstructed of ferrous sheet metal having high magnetic permeabilitywith the aid of punches and dies, and the adjacent annular inner andouter flanges of the coaxial pole-pieces are segregated from each otherby rings 24, 25 respectively, formed of non-magnetic material such asbrass. netic slugs or blocks H are of cylindrical shape and are clampedbetween the pole-pieces l5, l6 and attached to the plate I by means ofscrew bolts, but any desired number of these blocks ll of diverse shapesand sizes may be secured to the pole-pieces in any other suitablemanner. The core blocks 11 are preferably formed of material such asAlnico adapted to retain high magnetic energy when permanentlymagnetized, and when assembled as shown, these blocks I1 cooperate withthe pole-pieces I5, [6 to produce powerful fields of magnetic influencespanning the rings 24, 25 outwardly beyond the common plane of thepole-pieces.

When the improved ground clamp unit has been constructed and assembledas shown in Figs. -1, 2 and 3, the magnet assembly and its suspensionplate 1 will normally rest and float upon the helical spring l4, and thecontact surface of the terminal head l2 will be located outwardly beyondthe common plane of the pole faces. However, whenever the active facesof the polepieces l5, [6 are brought in proximity to a grounding memberor body 26, the magnetic fields which constantly span the segregatingrings 24, 25 will quickly clamp the pole-pieces to the body 23 and willforce the terminal l0 into the sleeve element *9 thereby compressing thehelical spring M and causing the outer surface of the terminal head E2to snugly engage the body 26, as illustrated in Fig. 2. Electric currentmay then be caused to flow through the conductor H and terminal ill; andwhen the flow of current has been interrupted, the terminal clamp may bereadily removed by moving or lifting the unit away from the surface ofthe body 26 sufficiently to remove the latter from the field of magneticinfluence.

While the terminal ll] of Figs. 1 to 3 inclusive is disposed centrallywithin and is surrounded by the relatively movable magnet assemblage,such As shown, the six magspecific disposition of the parts is notessential, and the magnet assembly may in fact be located within andsurrounded by an annular terminal.

as shown in the modification of Fig. 4. This modified ground clamp unitcomprises in general a circular backing plate 21 movably confined Withina recess 28 formed in an annular terminal 30, by means of a closure disk29; an annular series of helical compression springs 34 coacting withsockets 3| formed in the terminal recess 28 and reacting against theperipheral portion of the plate 21; outer and inner cup-shapedpolepieces 35, 36 respectively having flat annular pole faces lying in acommon plane, and coacting with the opposite ends of an annular seriesof ma netized cores or blocks 31; and a screw bolt 38 firmly attachingthe pole-pieces 35, 36 to the plate 21 and clamping this plate to theintervening blocks 31.

The backing plate 21 of the modification may also be formed of durableelectrical insulation, and is spaced from the closure disk 29 a distancesufiicient to permit the annular, contact surface of the terminal 30 tobe forced downwardly beyond the common plane of the pole faces of thepole-pieces 35, 36, by the compression springs 34,: when the magnets areinactive. The annular terminal 30 is preferably formed of copper orcopper alloy and may also be provided with a silver covered contactsurface, and this terminal 33 has an integral terminal socket 39 towhich the flexible conductor II is attachable in any suitable manner.The helical springs 34 are re tained in proper position by the sockets3|; and the cup-shaped pole-pieces 35, 36 are preferably formed of sheetmetal having high magnetic per; meability, while the blocks 31 areformed of material adapted to retain high magnetic energy Whenpermanently magnetized, and may be fastened to the pole-pieces 35, 36with the aid of screws or rivets 40 passing centrally through theblocks. The cooperating pole-pieces 35, 36 are segregated from eachother by a non-magnetic inner ring 4|, and the outer pole-piece 35 isspaced from the terminal 30 but is guided for movement therein by anouter non-magnetic ring 42, the latter being formed of electricalinsulation.

The normal operation and use of the modified ground clamp issubstantially like that of Figs. 1, 2, and 3, and the magnetized. blocks3'! constantly create magnetic fields spanning the spacer ring 4|onwardly of the common plane of the annular coaxial pole faces ofpole-pieces 35, 36. However, when these fields are brought in closeproximity to a grounding body 26, the magnet assemblage quickly becomeseffective to compress the springs 34 and to clamp the annular terminalinto snug engagement with the body 26, as depicted in Fig. 4. Electriccurrent may then be passed from the conductor ll through the terminal 30to the grounding body 26; and upon interruption of the current, theterminal clamp may be readily removed by merely lifting or moving theunit away from the magnetic surface of the body 26 a distance suflicientto remove this body from the field of magnetic influence.

It is to be noted that in both embodiments of the invention illustrated,the magnet assemblage is normally floating upon the compression springswhich are supported by thetermlnal, so that the common plane of theannular magnet pole faces will in each case adjust itself toirregularities of the contacted body 26. The compression springs tend tomove the terminal toward or against the grounding body 26 while themagnets tend to means:

,pull this body toward the fterminalythusrpro- ,ducing opposing forceswhich partially counter act each other and thereby make .it relatively:easy to release the clamping effect induced by the more powerfulmagnetic force. In each case, the cooperating coaxial annularpole-pieces provide extensive fields of magnetic influence, and in bothembodiments the permanently magnetized blocks are concealed andprotected within the cup-shaped pole-pieces. The helical springs of bothtypes are also well concealed and protected, :andin each embodiment ofthe invention sufiicient clearance should be provided between theterminal and the magnet assemblage to permit slight relative rocking ofthese parts.

vFrom the'foregoing detailed description of several embodiments of myinvention, it should be apparent that I have provided an improved groundterminal clamping unit which besides being exceedingly simple, compactand durable in construction, is also highly efiective in use andflexible in its adaptations. The various parts of theimproved clampassemblage are obviously simple but durable and may be readily assembledor dismantled. The use of Alnico metal in the permanently magnetizedblocks of the magnet assembly, insures prpduction of a powerful magneticfield, and the use of the cup-shaped pole-pieces enables concentration.of the field of magnetic influence throughout extensive annular areaswhich are disposed coaxial with the ground terminals. The floating,spring suspension of the magnet also permits the pole faces to adjustthemselves for proper cooperation with grounding bodies 26 of variousshapes, and as previously indicated, any desired number of thepermanently magnetized cores or blocks of diverse shapes may beutilized. It is however important that the current carrying conductorsI0, 30 be insulated from the magnet assemblies in order to positivelyprevent the current from passing through the adjacent polepieces I5, ofthe magnets, since such flow of the current will burn the pole faceedges and will thus prevent the springs I4, 34 from functioningproperly. The invention has proven highly satisfactory in actual useespecially as applied to welders ground clamps, although the improvedfeatures may also be utilized for other terminal clamping purposes.

It should be understood that it is not desired to limit this inventionto the exact details of construction or to the precise mode of use, ofthe clamps herein specifically shown and described, for variousmodifications within the scope constantlyfurgingthe conducting :meanscute wardly beyond thexplaneof-said pole faces.

12.1-In .amagnetic clamp, electric current con-.- ducting means disposedsymmetrically with respect to an axis, inner and outer circular polepieces confined one within the other coaxially of said axis, means forsuspending and insulating said pole pieces from said conducting means,said pole pieces having spaced flat portions provided with concentriccylindrical tubular flanges spaced from each other andprovided at theiradjacent free edges with annular flat pole faces disposed in a commonplane perpendicular to said axis, an annular group of permanentlymagnetized blocks contacting and secured between said fiat portionsbetween said inner and outer pole pieces, and means interposed'betweensaid conducting means and the outer-of said pole pieces for constantlyresiliently urging the conducting means outwardly beyond the plane ofsaid pole faces.

3. In a magnetic clamp, electric current conducting meansdisposedsymmetrically-with respect to an axis,'inner and outer annularpole pieces confined one within the other coaxially of said axis, meansfol-uniting and for insulating said pole pieces from said conductingmeans, said pole pieces having spaced parallel fiat portions providedwith integral concentric tubular flanges spaced from each other and saidflanges being provided at their adjacent free edges with annular polefaces disposed in a common plane perpendicular to said axis, an annulargroup of permanently magnetized blocks confined in the space betweensaid flat inner and outer pole piece portions, and spring meansinterposed between said conducting means and said outer pole piece forconstantly resiliently urging the conducting means outwardly beyond theplane of said pole disposed in a common plane perpendicular to saidaxis, an annular group of permanently magnetized blocks contacting andsecured between said fiat portions of both of said pole pieces, and

of th appended claims may occ t person spring means interposed betweensaid conductskilled in the art; and it is also contemplated thatspecific descriptive terms used herein be given the broadest possibleinterpretation consistent with the actual disclosure.

I claim:

1. In a magnetic clamp, electric current conducting means disposedsymmetrically with respect to an axis, inner and outer annular polepieces confined one within the other coaxially of ing means and saidouter pole piece for constantly urging the conducting means outwardlybeyond the plane of said pole faces.

5. In a magnetic clamp, electric current conducting means disposedsymmetrically with respect to an axis, inner and outer annular polepieces confined one within the other concentrically of each other aroundsaid conducting means coaxially of said axis, means for suspendsaidaxis, means for suspending and insulating 66 mg Said p018 Pieces fromSaid conducting means,

said pole-pieces from said conducting means, said pole pieces havingspaced flat portions provided with concentric tubular flanges spacedfrom each other and provided at their adjacent free said pole pieceshaving spaced flat portions provided with concentric tubular flangesspaced from each other and provided at their adjacent free edges withannular pole faces disposed in a edges with annular pole faces disposedin a com- 70 c m on plane p pendicular to said axis, an

mon plane perpendicular to said axis, an annular group of magnetizedblocks contacting and confined between the flat portions of said innerand outer pole pieces, and means interposed between annular group ofpermanently magnetized blocks contacting and secured to the adjacentsurfaces of both of said flat pole piece portions, spring meansinterposed between said conductin means said conducting means and saidpole pieces for and said outer Pole piece for constantly ur ng theconducting means outwardly beyond the plane of said pole faces, and aninsulation member between the inner periphery of said outer pole pieceand said conducting means for guiding the latter for movementlongitudinally of said axis.

6. In a magnetic clamp, annular electric current conducting meansdisposed symmetrically with respect to an axis, inner and outer annularpole pieces confinedone within the other concentrically of each otherwithin said conducting means coaxially of said axis, means forsuspending and for insulating said pole pieces from said conductingmeans, said pole pieces having spaced flat portions provided withconcentric tubular flanges spaced from each other and provided at theiradjacent free edges with annular pole faces disposed in a common planeperpendicular to said axis, an annular group of permanently magnetizedblocks contacting, and secured to the spaced fiat portions of both ofsaid pole pieces,

and sprin means interposed between said 0011- ducting means and saidouter pole piece for constantly urging the annular conducting meansoutwardly beyond the plane of said pole faces.

'7. In a magnetic clamp, annular electric current conducting meansdisposed symmetrically with respect to an axis, inner and outer annularpole pieces confined one within th other concentrically of each otherwithin said conducting means coaxially of said axis, means for retainingsaid pole pieces within said conducting means, said pole pieces havingspaced fiat portions provided with concentric tubular flanges spacedfrom each other and provided at their adjacent free edges with annularpole faces disposed in a common plan perpendicular to said axis, anannular group of permanently magnetized blocks contacting and securedwithin the space between said flat pole piece portions, spring meansinterposed between said conducting means and said outer pole piece forconstantly urging the annular conducting means outwardly beyond theplane of said pole faces, and an insulation member between the outerperiphery of said outer pole piece and said annular conducting means forguiding the latter for movement along said axis.

KARL A. BLIND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,105,552 Downes July 28, 19141,561,554 Little Nov. 17, 1925 1,778,481 Boucher Oct. 14, 1930 2,083,845Hovious June 15, 1937 2,170,287 Kinnebraw Aug. 22, 1939 2,287,112 LourieJune 23, 1942 2,312,083 Diane Feb. 23, 1943 2,429,526 Savon Oct. 21,1947 2,437,633 Abram Mar. 9, 1948

